Constructing electron-enriched Co tetrahedral sites to promote oxygen electrocatalysis in rechargeable zinc-air batteries

Abstract

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key performance-limiting step of rechargeable zinc-air batteries. Developing a reliable strategy to optimize the activity of Co occupied the tetrahedral site (Coth) is crucial for enhancing electrocatalytic performance and still needs further elaborate elucidation. Here, Mo dopants were used as electron donors to construct low-valence Coth sites in cobalt phosphide, resulting in downshifted d-band centers and strengthened hybridization between Co 3d and P 3p orbitals. The negative charges are easier to accumulate on three antibonding orbitals of Coth, promoting the desorption of oxygen intermediates, as evidenced using density functional theory calculations and in-situ spectroscopic investigations. The optimal catalyst delivers impressive ORR and OER performance, in terms of half-wave potential of 0.84 V for ORR and overpotential of 247 mV for OER. In general, this work opens a new opportunity to rationally regulate electronic structure of Coth sites via introducing an electron donor, as well as provides guidance for exploring electronic descriptors of tetrahedral sites.